12,272 research outputs found
Posterior Mean Super-Resolution with a Compound Gaussian Markov Random Field Prior
This manuscript proposes a posterior mean (PM) super-resolution (SR) method
with a compound Gaussian Markov random field (MRF) prior. SR is a technique to
estimate a spatially high-resolution image from observed multiple
low-resolution images. A compound Gaussian MRF model provides a preferable
prior for natural images that preserves edges. PM is the optimal estimator for
the objective function of peak signal-to-noise ratio (PSNR). This estimator is
numerically determined by using variational Bayes (VB). We then solve the
conjugate prior problem on VB and the exponential-order calculation cost
problem of a compound Gaussian MRF prior with simple Taylor approximations. In
experiments, the proposed method roughly overcomes existing methods.Comment: 5 pages, 20 figures, 1 tables, accepted to ICASSP2012 (corrected
2012/3/23
Machine Learning for Fluid Mechanics
The field of fluid mechanics is rapidly advancing, driven by unprecedented
volumes of data from field measurements, experiments and large-scale
simulations at multiple spatiotemporal scales. Machine learning offers a wealth
of techniques to extract information from data that could be translated into
knowledge about the underlying fluid mechanics. Moreover, machine learning
algorithms can augment domain knowledge and automate tasks related to flow
control and optimization. This article presents an overview of past history,
current developments, and emerging opportunities of machine learning for fluid
mechanics. It outlines fundamental machine learning methodologies and discusses
their uses for understanding, modeling, optimizing, and controlling fluid
flows. The strengths and limitations of these methods are addressed from the
perspective of scientific inquiry that considers data as an inherent part of
modeling, experimentation, and simulation. Machine learning provides a powerful
information processing framework that can enrich, and possibly even transform,
current lines of fluid mechanics research and industrial applications.Comment: To appear in the Annual Reviews of Fluid Mechanics, 202
Single Frame Image super Resolution using Learned Directionlets
In this paper, a new directionally adaptive, learning based, single image
super resolution method using multiple direction wavelet transform, called
Directionlets is presented. This method uses directionlets to effectively
capture directional features and to extract edge information along different
directions of a set of available high resolution images .This information is
used as the training set for super resolving a low resolution input image and
the Directionlet coefficients at finer scales of its high-resolution image are
learned locally from this training set and the inverse Directionlet transform
recovers the super-resolved high resolution image. The simulation results
showed that the proposed approach outperforms standard interpolation techniques
like Cubic spline interpolation as well as standard Wavelet-based learning,
both visually and in terms of the mean squared error (mse) values. This method
gives good result with aliased images also.Comment: 14 pages,6 figure
The K2-ESPRINT Project III: A Close-in Super-Earth around a Metal-rich Mid-M Dwarf
We validate a planet on a close-in orbit
( days) around K2-28 (EPIC 206318379), a metal-rich
M4-type dwarf in the Campaign 3 field of the K2 mission. Our follow-up
observations included multi-band transit observations from the optical to the
near infrared, low-resolution spectroscopy, and high-resolution adaptive-optics
(AO) imaging. We perform a global fit to all the observed transits using a
Gaussian process-based method and show that the transit depths in all passbands
adopted for the ground-based transit follow-ups () are within of the K2 value. Based on a model of
the background stellar population and the absence of nearby sources in our AO
imaging, we estimate the probability that a background eclipsing binary could
cause a false positive to be . We also show that K2-28
cannot have a physically associated companion of stellar type later than M4,
based on the measurement of almost identical transit depths in multiple
passbands. There is a low probability for a M4 dwarf companion (), but even if this were the case, the size of K2-28b
falls within the planetary regime. K2-28b has the same radius (within
) and experiences a similar irradiation from its host star as the
well-studied GJ~1214b. Given the relative brightness of K2-28 in the near
infrared ( mag and mag) and relatively deep
transit (), a comparison between the atmospheric properties of these
two planets with future observations would be especially interesting.Comment: 11 pages, 9 figures, accepted to Ap
Efficient Active Learning for Image Classification and Segmentation using a Sample Selection and Conditional Generative Adversarial Network
Training robust deep learning (DL) systems for medical image classification
or segmentation is challenging due to limited images covering different disease
types and severity. We propose an active learning (AL) framework to select most
informative samples and add to the training data. We use conditional generative
adversarial networks (cGANs) to generate realistic chest xray images with
different disease characteristics by conditioning its generation on a real
image sample. Informative samples to add to the training set are identified
using a Bayesian neural network. Experiments show our proposed AL framework is
able to achieve state of the art performance by using about 35% of the full
dataset, thus saving significant time and effort over conventional methods
The Perception-Distortion Tradeoff
Image restoration algorithms are typically evaluated by some distortion
measure (e.g. PSNR, SSIM, IFC, VIF) or by human opinion scores that quantify
perceived perceptual quality. In this paper, we prove mathematically that
distortion and perceptual quality are at odds with each other. Specifically, we
study the optimal probability for correctly discriminating the outputs of an
image restoration algorithm from real images. We show that as the mean
distortion decreases, this probability must increase (indicating worse
perceptual quality). As opposed to the common belief, this result holds true
for any distortion measure, and is not only a problem of the PSNR or SSIM
criteria. We also show that generative-adversarial-nets (GANs) provide a
principled way to approach the perception-distortion bound. This constitutes
theoretical support to their observed success in low-level vision tasks. Based
on our analysis, we propose a new methodology for evaluating image restoration
methods, and use it to perform an extensive comparison between recent
super-resolution algorithms.Comment: CVPR 2018 (long oral presentation), see talk at:
https://youtu.be/_aXbGqdEkjk?t=39m43
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